Comparative Hydro-Mechanical Response of Marl and Chikoko Soils from the Niger Delta to Multiple Wetting and Drying Cycles

This study compares how two different but common soil types—Marl and Chikoko soils—respond to various cycles of wetting and drying. In a three-level, four-factor full factorial design framework, these soils—Marl, a calcareous clay, and Chikoko, an organic-rich swampy clay—were all subjected to a rigorous experimental program using standard and modified oedometer tests. Their volumetric changes, deformation characteristics, and tensile strength properties were carefully compared in the investigation under various conditions, including changes in initial moisture content, dry density, surcharge pressure, and the number of wetting and drying cycles. The main conclusions show that although both soils are highly susceptible to cracking and show considerable volumetric instability, their specific reactions, accumulation of cumulative strain, and patterns of degradation are very different. While Chikoko soil exhibits complex, frequently larger magnitude, volumetric changes and greater susceptibility to structural degradation influenced by its organic content, Marl soil typically exhibits more classical expansive clay behavior with noticeable swell. A monolithic approach to geotechnical engineering in the Niger Delta is discouraged by the study, which emphasizes that the best design strategies for preventing moisture-induced damage in the area must be specifically tailored to the distinct hydro-mechanical profile of each soil type. This comparative understanding is essential for creating infrastructure solutions that are more sustainable and resilient.